Low viscosity, high particulate loading dispersions

ABSTRACT

The present invention relates to dispersions comprising particulate materials and a solvent, with an optional dispersant. The solvent has a low dielectric constant, and the particulate material is present at high loading levels. The resulting dispersion has been found to be stable and have a low viscosity, even at high particulate material loadings. Various uses for these dispersions are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional PatentApplication No. 60/800,630, filed May 16, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to low viscosity dispersions comprisingparticulate material and a solvent.

2. Description of the Related Art

Pigments are finely divided, insoluble, solid particles which are, ingeneral, not readily dispersible alone in liquid vehicles. A variety oftechniques have been developed which can provide stable pigmentdispersions. For example, dispersants can be added to the pigment toimprove its dispersibility in a particular medium. Examples ofdispersants include water-soluble polymers and surfactants.

The choice of dispersant depends on a variety of factors, including themorphological and chemical properties of the pigment and the type ofliquid vehicle (resin or binder and solvent) in which the pigment is tobe dispersed. However, the dispersant can often have a negative impacton properties such as color development and viscosity. This isparticularly true at high pigment loading levels, such as greater than10% pigment. For example, high surface area pigments are generallydifficult to disperse without a high level of dispersant, but such ahigh level of dispersant often results in an unacceptable increase inthe dispersion viscosity. Therefore, the amount of dispersant must beadjusted for the components used in order to obtain dispersioncompositions with good overall properties.

Modified pigments, including modified colored pigments, have also beendeveloped which provide dispersible pigment compositions, such as inksand coatings, with improved properties. For example, U.S. Pat. No.5,851,280 discloses methods for the attachment of organic groups ontopigments including, for example, attachment via a diazonium reactionwherein the organic group is part of the diazonium salt. The resultingsurface-modified pigments can be used in a variety of applications, suchas inks, inkjet inks, coatings, toners, plastics, rubbers, and the like.U.S. Pat. No. 5,885,335 describes the use of modified pigments havingattached ionic and/or ionizable groups at specified levels in aqueousand non-aqueous ink and coating compositions. Also, U.S. Pat. Nos.5,713,988 and 5,698,0916 describe modified pigments having various typesof attached groups that can be used in non-aqueous inks and coatings.Furthermore, PCT International Publication No. WO 01/51566 describes amethod of making a modified pigment by reacting a first chemical groupand a second chemical group to form a pigment having attached a thirdchemical group. The first chemical group includes at least onenucleophile and the second chemical group includes at least oneelectrophile, or vice versa. This method may be used, for example, toprepare modified pigments having attached polymeric groups, which can beused in ink compositions and, in particular, inkjet ink compositions.

However, while these methods can be used to produce ionically modifiedpigments that can be dispersed in various types of non-aqueouscompositions, it would be expected that these compositions would havehigh viscosity, particularly at high loading levels, in non-aqueoussolvents. The reason for this is that the chargeable groups attached tothe pigments would not be expected to be charged in a non-aqueous systemand would therefore interact with each other, thereby increasing theviscosity. While such high viscosity systems may be useful in someapplications, lower viscosity is generally more desirable since, forexample, they are easier to process and can be applied using multipletechniques, including inkjet printing, dip coating, etc.

Therefore, while these methods provide dispersions of pigments,including modified pigments having attached groups, there remains a needfor pigment dispersions, particularly those having high loadings ofpigment, having improved performance properties, such as viscosity,thereby providing advantageous alternatives to previous modifiedpigments.

SUMMARY OF THE INVENTION

The present invention relates to a dispersion comprising a particulatematerial and a solvent. The particulate material is present in an amountof ≧25% by weight based on the total weight of the dispersion, thesolvent has a dielectric constant of ≦50; and the dispersion has aviscosity of ≦50 cP.

The present invention further relates to a dispersion comprising aparticulate material, a dispersant, and a solvent. The particulatematerial is an oxidized carbonaceous material or a modified pigmentcomprising a pigment having attached at least one ionic group, at leastone ionizable group, or a mixture thereof, and this is present in anamount of ≧10% by weight based on the total weight of the dispersion.The dispersant forms associative structures in the solvent, which has adielectric constant of ≦50, and the dispersion has a viscosity of ≦50cP.

The present invention further relates to a dispersion comprising aparticulate material, a dispersant, and a solvent. The particulatematerial is an oxidized carbonaceous material or is a modified pigmentcomprising a pigment having attached at least one ionic group, at leastone ionizable group, or a mixture thereof. The dispersant formsassociative structures in the solvent, and the dispersion furthercomprises associative structures of the dispersant. The solvent has adielectric constant of ≦50, and the dispersion has a viscosity of ≦50cP.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the presentinvention, as claimed.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to dispersions of particulate materials ina solvent. The dispersions have low viscosity even at high loadinglevels of particulate material. Preferably, the viscosity of thedispersion is ≦50 cP and can be measured using any method known in theart.

The particulate material used in the dispersions of the presentinvention may be organic, inorganic, or a combination of both. Forexample, the particulate material may be any type of pigmentconventionally used by those skilled in the art for inks, coatings, andthe like, such as carbonaceous pigments and organic colored pigmentsincluding pigments comprising a blue, black, brown, cyan, green, white,violet, magenta, red, orange, or yellow pigment. Mixtures of differentpigments can also be used. Examples of suitable carbonaceous pigmentsinclude carbon products such as graphite, carbon black, vitreous carbon,carbon fibers, activated charcoal, activated carbon, and carbonnanotubes. The carbon may be of the crystalline or amorphous type.Finely divided forms of the above are preferred; also, it is possible toutilize mixtures of different carbons. Of these carbon products, carbonblack is preferred.

Representative examples of carbonaceous pigments include various carbonblacks (Pigment Black 7) such as channel blacks, furnace blacks and lampblacks, and include, for example, carbon blacks sold under the Regal®,Black Pearls®, Elftex®, Monarch®, Mogul®, and Vulcan® trademarksavailable from Cabot Corporation (such as Black Pearls® 2000, BlackPearls® 1400, Black Pearls® 1300, Black Pearls® 1100, Black Pearls®1000, Black Pearls® 900, Black Pearls® 880, Black Pearls® 800, BlackPearls® 700, Black Pearls® L, Elftex® 8, Monarch® 1400, Monarch® 1300,Monarch® 1100, Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800,Monarch® 700, Mogul® L, Regal® 330, Regal® 400, Vulcan® P). Suitableclasses of organic colored pigments include, for example,anthraquinones, phthalocyanine blues, phthalocyanine greens, diazos,monoazos, pyranthrones, perylenes, heterocyclic yellows,quinolonoquinolones, quinacridones, and (thio)indigoids. Such pigmentsare commercially available in either powder or press cake form from anumber of sources including, BASF Corporation, Engelhard Corporation andSun Chemical Corporation. Examples of other suitable colored pigmentsare described in the Colour Index, 3rd edition (The Society of Dyers andColourists, 1982).

The particulate material may also be a carbonaceous material such ascarbon black that has been oxidized using an oxidizing agent in order tointroduce ionic and/or ionizable groups onto the surface. Any of thecarbon blacks described above can be used. Oxidized carbonaceouspigments, such as oxidized carbon blacks, prepared in this way have beenfound to have a higher degree of oxygen-containing groups on thesurface. Oxidizing agents include, but are not limited to, oxygen gas,ozone, peroxides such as hydrogen peroxide, persulfates, includingsodium, potassium, or ammonium persulfate, hypohalites such a sodiumhypochlorite, oxidizing acids such a nitric acid, and transition metalcontaining oxidants, such as permanganate salts, osmium tetroxide,chromium oxides, or ceric ammonium nitrate. Mixtures of oxidants mayalso be used, particularly mixtures of gaseous oxidants such as oxygenand ozone. In addition, carbonaceous pigments, such as carbon black,prepared using other surface modification methods to introduce ionic orionizable groups onto a pigment surface, such as chlorination andsulfonylation, may also be used.

The particulate material may also be a modified pigment comprising apigment having attached at least one organic group, wherein the organicgroup comprises at least one ionic group, at least one ionizable group,or a mixture thereof. The pigment of the modified pigment may be any ofthose described above. Preferably the organic group is directlyattached. The modified pigments may be prepared using any method knownto those skilled in the art such that organic chemical groups areattached to the pigment. For example, the modified pigments can beprepared using the methods described in U.S. Pat. Nos. 5,554,739,5,707,432, 5,837,045, 5,851,280, 5,885,335, 5,895,522, 5,900,029,5,922,118, and 6,042,643, and PCT Publication WO 99/23174, thedescriptions of which are fully incorporated herein by reference. Suchmethods provide for a more stable attachment of the groups onto thepigment compared to dispersant type methods, which use, for example,polymers and/or surfactants. Other methods for preparing the modifiedpigments include reacting a pigment having available functional groupswith a reagent comprising the organic group. Such modified pigments maybe prepared using the methods described in the references incorporatedabove. In addition modified carbon blacks containing functional groupsmay also be prepared by the methods described in U.S. Pat. Nos.6,831,194 and 6,660,075, U.S. Patent Publication Nos. 2003-0101901 and2001-0036994, Canadian Patent No. 2,351,162, European Patent No. 1 394221, and PCT Publication No. WO 04/63289, each of which is alsoincorporated in their entirety by reference herein.

The attached organic group is chosen depending on a variety of factors,including the specific type of solvent as well as the intended use ofthe dispersion. This allows for greater flexibility by tailoringproperties of the modified pigment dispersion. The organic groupcomprises at least one ionic group, at least one ionizable group, or amixture of at least one ionic group and at least one ionizable group. Anionic group is either anionic or cationic and is associated with acounterion of the opposite charge including inorganic or organiccounterions such as Na⁺, K⁺, Li⁺, NH₄ ⁺, NR′₄ ⁺ acetate, NO₃ ⁻, SO₄ ⁻²,OH⁻, and Cl⁻, where R′ represents hydrogen or an organic group such as asubstituted or unsubstituted aryl and/or alkyl group. An ionizable groupis one that is capable of forming an ionic group in water and is, tosome extent, associated with its counterion in a medium of low polarity,unless additives are used to disassociate the counterion. Anionizablegroups form anions and cationizable groups form cations. Thus, theorganic group is an organic ionic or ionizable group. Such groupsinclude those described in U.S. Pat. No. 5,698,016, the description ofwhich is fully incorporated herein by reference.

For example, the modified pigment may comprise a pigment having attachedat least one anionic group, which is a negatively charged ionic group.Anionic groups may be generated from groups having ionizablesubstituents that can form anions, such as acidic substituents, or maybe the anion in the salts of ionizable substituents. Representativeexamples of anionic groups include —COO⁻, —SO₃ ⁻, —OSO₃ ⁻, —HPO₃ ⁻,—OPO₃ ⁻², and —PO₃ ⁻². Representative examples of anionizable groupsinclude —COOH, —SO₃H, —PO₃H₂, —R′SH, —R′OH, and —SO₂NHCOR′, where R′represents hydrogen or an organic group such as a substituted orunsubstituted aryl and/or alkyl group. Preferably, the attached groupcomprises a carboxylic acid group, a sulfonic acid group, a sulfategroup, or salts thereof. For example, the attached group may be anorganic group such as a benzene carboxylic acid group, a benzenedicarboxylic acid group, a benzene tricarboxylic acid group, a benzenesulfonic acid group, or salts thereof. Specific organic ionic groups are—C₆H₄—CO₂H, —C₆H₄SO₃H, or salts thereof. The attached organic group mayalso be a substituted derivative of any of these.

As another example, the modified pigment may comprise a pigment havingattached at least one cationic group, which is a positively chargedorganic ionic group that may be generated from ionizable substituentsthat can form cations (cationizable groups), such as protonated amines.For example, alkyl or aryl amines may be protonated in acidic media toform ammonium groups —NR′₂H⁺, where R′ represent an organic group suchas a substituted or unsubstituted aryl and/or alkyl group. Cationicgroups may also be positively charged organic ionic groups. Examplesinclude quaternary ammonium groups (—NR′₃ ⁺) and quaternary phosphoniumgroups (—PR′₃ ⁺). Here, R′ represents hydrogen or an organic group suchas a substituted or unsubstituted aryl and/or alkyl group. Preferably,the attached group comprises an alkyl amine group or a salt thereof oran alkyl ammonium group.

The amount of attached groups can be varied depending on the solvent andthe desired properties of the dispersion. In general, the amount ofattached organic groups is from about 0.001 to about 10.0 micromoles oforganic group per square meter surface area of pigment (surface area asmeasured, for example, by nitrogen adsorption). Preferably, the amountof attached organic groups is between from about 0.1 to about 5.0micromoles/m², more preferably between from about 0.1 to about 4.0micromoles/m², and most preferably between from about 0.5 to about 3.0micromoles/m². The amount attached can be varied depending on thespecific attached group and can be adjusted depending on, for example,the size of the attached group or the functionality of the ionic group.Further, it is also within the scope of the present invention to havemore than one type of attached group, such as a non-ionic ornon-chargeable group, especially one capable of providing additionalsteric stabilization, on the modified pigment in order to provide forthe best overall performance. In this case, the amount of the ionic orionizable group is preferably greater than amount of the non-ionic group(on a molar basis).

The particulate material, such as a modified pigment or oxidizedcarbonaceous material, may be purified by washing, such as byfiltration, centrifugation, or a combination of the two methods, toremove unreacted raw materials, byproduct salts, and other reactionimpurities. The products may also be isolated, for example, byevaporation, including spray drying, or it may be recovered byfiltration and drying using known techniques to those skilled in theart. In addition, the particulate material, such as a modified pigmentor oxidized carbonaceous material, can be purified to remove anyundesired free species, such as unreacted treating agents used toprepare them. Known techniques of ultrafiltration/diafiltration using amembrane or ion exchange may be used to purify the particulate materialand remove a substantial amount of free ionic and unwanted species, ifpresent. Also, an optional exchange of counterions can be used if theparticulate material is a modified pigment or oxidized carbonaceousmaterial whereby the counterions that form a part of the modified oroxidized pigment can be exchanged or substituted with alternativecounterions (including, e.g., amphiphilic ions) utilizing known ionexchange techniques such as ultrafiltration, reverse osmosis, ionexchange columns and the like. Particular examples of counterions thatcan be exchanged include, but are not limited to, Na⁺, K⁺, Li⁺, NH₄ ⁺,Ca²⁺, Mg²⁺, Cl⁻, NO₃ ⁻, NO₂ ⁻, acetate, and Br⁻.

The particulate material used in the dispersion of the present inventioncan have a wide range of BET surface areas, as measured by nitrogenadsorption, depending on the desired properties of the dispersioncomprising the particulate material. As is known to those skilled in theart, a higher surface area will correspond to smaller particle size. Forcarbon black, this particle size is the aggregate particle size, whichis the smallest unit of carbon black that can be dispersed. If a highersurface area particulate material is not readily available for thedesired application, it is also well recognized by those skilled in theart that the particulate material may be subjected to conventional sizereduction or comminution techniques, such as media, ball or jet milling,to reduce the material to a smaller particle size, if desired.

The dispersion of the present invention further comprises at least onesolvent having a dielectric constant of ≦50. Suitable examples includealcohols, glycols, ethers (such as tetrahydrofuran or diethylether),ketones (such as acetone or methylethyl ketone), acetates (such as ethylacetate), amides (such as dimethylformamide), sulfoxides (such asdimethylsulfoxide), hydrocarbons, and miscible mixtures thereof. Thesolvent may also further comprise water. However, since the dielectricconstant of the solvent is low, the solvent is therefore not water alonenor is it a mixture comprising more than 50% by weight water. Thus, thesolvent is a non-aqueous solvent and may further comprise less than 50%by weight water, such as ≦40%, ≦30%, ≦20%, or ≦10% by weight water.

The amount of particulate material present in the dispersion of thepresent invention can be varied depending on, for example, the type ofparticulate material and the type of solvent. However, the dispersionsof the present invention are generally referred to as high loadingdispersions. By “high” is meant that the amount of particulate materialis ≧10% by weight based on the total weight of the dispersion. Forexample, the particulate material loading level may be ≧10%, ≧15%, ≧20%,≧25, or ≧30% by weight based on the total weight of the dispersion.Preferably, for some applications, the dispersion comprises ≧20% or,more preferably, ≧25% by weight particulate material.

In one embodiment of the present invention, the dispersion furthercomprises at least one dispersant which forms associative structures inthe solvent. By “associative structures” is meant an organizedarrangement of dispersant molecules resulting from the interaction ofgroups of the dispersant, such as inverse micelles. Examples of suitabledispersants include, but are not limited to, polyalkylene oxides (suchas polyethylene oxide or polypropylene oxide), polyesters (such aspolycaprolactone, polyvalerolactone, poly(hydroxy stearic acid), orpoly(hydroxyoleic acid), polyamides such as polycaprolactam,polyacrylates, and block copolymers having both a hydrophobic and ahydrophilic group. Additional examples include amine-functionalizedderivatives (such as polyamine, tertiary amine, or quaternary ammoniumfunctionalized derivatives) or acid functionalized derivatives (such ascarboxylic acid or phosphonic acid functionalized deriviatives) ofthese, such as amine-funtionalized or amine-terminated polyalkyleneoxides or acrylic polymers comprising amine or acid functional groups.Other suitable dispersants will be known to one skilled in the art orcould be identified by adding the dispersant to the solvent above itscritical micelle concentration (CMC) and determining if associativestructures, such as inverse micelles, have formed. Particularlypreferred are those dispersants that not only form associativestructures in the solvent but also form such structures in thedispersion itself—i.e., in the presence of the particulate material.Techniques such as light scattering methods known to one skilled in theart can be used to detect the presence of such structures in either thesolvent or in the dispersion.

For this embodiment, specific dispersants can be chosen based on thetype of particulate material and the desired overall properties of thedispersion. For example, if the particulate material is a modifiedpigment comprising a pigment having attached at least one organic group,the dispersant preferably comprises at least one functional group chosenfor the type of organic group attached to the pigment. For example, ifthe modified pigment comprises a pigment having attached at least oneanionic group, at least one anionizable group, or a mixture thereof, ithas been found that dispersants comprising at least one cationicfunctional group, at least one cationizable functional group, or amixture thereof can preferably be used to produce dispersions of thepresent invention. Specific combinations include modified pigmentshaving attached at least one carboxylic acid group, sulfonic acid group,or salt thereof and dispersants comprising at least one amine group orammonium group. However, it is also possible, for this type of modifiedpigment, to produce dispersions of the present invention with adispersant comprising at least one anionic functional group, at leastone anionizable functional group, or a mixture thereof. Furthermore, ifthe particulate material is a modified pigment comprising a pigmenthaving attached at least one cationic group, at least one cationizablegroup, or a mixture thereof, it has been found that dispersantscomprising at least one anionic functional group, at least oneanionizable functional group, or a mixture thereof can preferably beused to produce dispersions of the present invention. Finally, it hasalso been found that dispersants comprising at least one nonionicfunctional group (such as a polyether group) can be used to producedispersions of the present invention if the modified pigment comprises apigment having attached at least one ionic group, at least one ionizablegroup, or a mixture thereof.

The amount of dispersant can be varied depending on the type ofparticulate material, the solvent, and the loading level of particulatematerial. In general, the ratio of the amount of dispersant to theamount of pigment can be between about 0.01 to 1 up to about 2.5 to 1and preferably is between about 0.1 to 1 up to about 1 to 1. While theuse of a dispersant is optional, it has been found that dispersants thatform associative structures in the solvent and, in particular, thosethat form the associative structures in the dispersion, can impartimproved properties, such as stability and low viscosity, to the highloading dispersions of the present invention. This is also true evenwhen the level of dispersant is high.

Thus, as described herein, the present invention relates to dispersionscomprising a particulate material and a low dielectric constant solvent,with an optional dispersant, wherein the level of the particulatematerial is high and wherein the viscosity of the dispersion is low. By“dispersion” is meant a two-phase system comprising finely dividedparticles distributed throughout a liquid phase. These dispersions havealso been found to be stable dispersions. By “stable” is meant that thedispersion properties do not change appreciably over time and/or withchanges in a specific condition. The dispersion of particulate materialremains a dispersion. Thus, for example, the particle size of theparticulate material in the dispersion can be below 500 nm, preferablybelow 300 nm, more preferably below 200 nm, and most preferably below150 nm, and this particle size does not change appreciably over time orwith variations in temperature, even at the high particulate materialloading levels described above. As discussed above, if the particulatematerial is a carbon black based pigment, the particle size wouldcorrespond to the aggregate particle size. As another example, thedispersion of the present invention does not develop high levels ofprecipitate over time. Thus, the solids level of the dispersion remainsessentially unchanged. Therefore, it has surprisingly been found thatstable high loading dispersions of particulate material can be formed ina low dielectric constant solvent (such as ≦50). It has further beenfound that such dispersions can be formed having a viscosity that is ≦50cP, even when the particulate material loading level is high, including≧10% by weight. This is particularly surprising for the embodiment ofthe invention in which the particulate material is an ionically modifiedparticle, such as an oxidized carbonaceous material or a modifiedpigment comprising a pigment having attached at least one ionic orionizable group. As noted above, it would be expected that thesecompositions would have high viscosity, particularly at high loadinglevels, in non-aqueous solvents since the chargeable groups attached tothe pigments would not be expected to be charged in a non-aqueoussystem. These pigments would therefore be expected to interact with eachother, thereby increasing the viscosity of the dispersion, particularlyover time. Instead, it has been found that the viscosity of thesedispersions is low and that this viscosity does not change appreciablyover time.

The dispersions of the present invention can be prepared using anymethod known in the art. For example, the particulate material andsolvent may be combined with agitation to produce a stable dispersion,and, if used, a dispersant may be added. Also, if the particulatematerial is dispersible in water, the aqueous solvent of this dispersionof the particulate material may be exchanged for the solvent of thedispersion. Examples of solvent exchange methods includediafiltration/ultrafiltration and addition of the solvent duringevaporation of the aqueous solvent. Alternatively, if a dispersant isused, this can be combined with the particulate material, and theresulting combination can then be combined with the solvent. Thepigment, dispersant, and solvent may be combined in any equipment knownin the art, such as a media or ball, or other high shear mixingequipment. Various conventional milling media can be used. Other methodsfor forming the dispersion of the present invention will be known to oneskilled in the art.

The dispersions of the present invention may be further purified orclassified to remove impurities and other undesirable free species whichcan co-exist in the dispersion as a result of the manufacturing process.For example, the dispersions can be subjected to a classification step,such as filtration, microfiltration, or centrifugation, to substantiallyremove particles having a size above about 1.0 micron. The removal ofimpurities from the dispersions may also improve the performance ofthese dispersions when used in various applications, including, forexample, ink compositions, coating compositions, or compositions used toprepare black matrices.

Therefore, the present invention further relates to compositionscomprising the dispersions of the present invention. For example, thedispersions may be used in plastic compositions, non-aqueous inks orcoatings, rubber compositions, paper compositions and textilecompositions. In particular, these pigments may be used in non-aqueouscompositions, including, for example, automotive and industrialcoatings, conductive coatings, coating compositions for preparing masksor temporary masks in the preparation of imaged articles, paints,toners, adhesives, and inks, such as non-aqueous inkjet inkcompositions, including industrial inkjet applications.

For example, the present invention further relates to a non-aqueous inkcomposition, such as a non-aqueous inkjet ink composition, comprisingthe dispersion of the present invention. The amount of dispersion usedcan be any amount such that the particulate material, such as a pigment,is present in the ink composition in an amount effective to provide thedesired image quality (for example, optical density) withoutdetrimentally affecting the performance of the ink. Typically, thedispersion is used in an amount such that the particulate material ispresent in an amount as low as about 0.1% by weight, preferably 0.5% byweight, and as high as about 30% by weight, preferably 25% by weightbased on the weight of the ink. Suitable additives may also beincorporated in order to impart a number of desired properties whilemaintaining the stability of the dispersion and the resulting inkcomposition. For example, conventional surfactants and/or dispersants,humectants, drying accelerators, penetrants, cosolvents, and binders, aswell as other additives known in the art, may be added. The amount of aparticular additive will vary depending on a variety of factors butgenerally ranges between 0% and 40% by weight based on the total weightof the ink composition. It is also within the bounds of the presentinvention to use a mixture of dispersions of the present invention,comprising different particulate materials, as well as mixtures of thedispersions of the present invention and conventional dispersions ofparticulate materials.

The present invention also further relates to a non-aqueous coatingcomposition, such as a curable coating composition, comprising thedispersion of the present invention. In one embodiment, such a coatingcomposition may be used to prepare a black matrix, particularly theblack matrix of the present invention, described in more detail belowused, which can be used, for example, in the color filter of a liquidcrystal display device. Also, if the particular material comprises anorganic colored pigment, the coating composition may be used to preparethe color filter itself. The coating composition preferably furthercomprises a resin, such as a curable resin. Also, conventionalcosolvents may also be added, such as butyl acetate, ethylcellosolve,ethylcellosolve acetate, butylcellosolve, butylcellosolve acetate,ethylcarbitol, ethylcarbitol acetate, diethyleneglycol, cyclohexanone,propyleneglycol monomethylether, propyleneglycol monomethyletheracetate, lactate esters, and mixtures thereof. Aqueous solvents may alsobe added, including, for example, water and water soluble alcohols, butthe amount of water will be below 50% by weight.

The curable resin may be any resin known in the art. For example, theresin may be an epoxy bisphenol-A resin or an epoxy novolac resin. Theresin may also be an acrylic resin, a polyimide resin, a urethane resin,a polyester resin, cellulose, or a gelatin. The resin is one that may becured thermally or by any source of radiation such as, for example,infrared or ultraviolet radiation. In this way, the curable coatingcomposition may be photosensitive (i.e. may be cured by irradiation) orthermosensitive (i.e., may be cured by changing temperature, such as byheating). When the resin is curable by irradiation, the curable coatingcomposition may further comprise a photoinitiator, which generates aradical on absorbing light with the respective pigment. Also, monomers,such as acrylates, methacrylates, epoxides, or styrenics, may beincluded.

The curable coating composition can be formed with a minimum ofadditional components (additives and/or cosolvents) and processingsteps. However, additives such as surfactants and cosolvents may also beincluded. For example, when a photosensitive resin is used, such asepoxy bisphenol-A or epoxy novolak, a photoinitiator can also be added.Monomers and/or oligomers may also be added.

The coating composition can be used to prepare a black matrix that canbe used, for example, for a color filter in a liquid crystal displaydevice. Thus, the present invention further relates to a black matrixcomposition comprising the dispersions of the present invention. Theblack matrix can be formed using any method known in the art. Forexample, the black matrix may be formed by applying the black matrixcomposition comprising a modified pigment onto a substrate, curing theresulting curable coating imagewise, and developing and drying the curedcoating.

The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature.

EXAMPLES

Examples 1-12 describe the preparation of dispersions of the presentinvention.

Example 1

20.0 g of a modified colored pigment (prepared by drying Cab-O-Jet® 250Ccolored pigment dispersion, an aqueous dispersion of a modified pigmentcomprising a cyan pigment having attached sulfonic acid groupscommercially available from Cabot Corporation), 6 g Disperbyk BYK163 (anamine-functionalized dispersant available from BYK Chemie), 13 g Joncryl611 (an acrylic copolymer available from Johnson Polymer, Inc.), and 61g butyl acetate as solvent were metered into a vessel. To this was added2 mm glass beads, and a dispersion was prepared by mixing on a Skandexmixer. The glass beads were removed using a paint strainer. Theviscosity of the dispersion (20% pigment loading) was measured using aBrookfield viscometer (spindle 000) and found to be 5.4 cP at 100 RPM.The mean volume particle size (mV) of the particulate material in thedispersion was measured using a Microtrac® Particle Size Analyzer andfound to be 0.67 μm. This dispersion, which included an acryliccopolymer, could be used as a non-aqueous coating composition.

Example 2

15.0 g of a modified colored pigment (prepared by drying Cab-O-Jet® 250Ccolored pigment dispersion, an aqueous dispersion of a modified pigmentcomprising a cyan pigment having attached sulfonic acid groupscommercially available from Cabot Corporation), 6 g Disperbyk BYK163 (anamine-functionalized dispersant available from BYK Chemie), 15 g Joncryl611 (an acrylic copolymer available from Johnson Polymer, Inc.), and 64g butyl acetate as solvent were metered into a vessel. To this was added2 mm glass beads, and a dispersion was prepared by mixing on a Skandexmixer. The glass beads were removed using a paint strainer. Theviscosity of the dispersion (15% pigment loading) was measured using aBrookfield viscometer (spindle 000) and found to be 7.2 cP at 100 RPM.The mean volume particle size (mV) of the particulate material in thedispersion was measured using a Microtrac® Particle Size Analyzer andfound to be 0.17 μm. This dispersion, which included an acryliccopolymer, could be used as a non-aqueous coating composition.

Example 3

15.0 g of a modified colored pigment (prepared using 2.4 mmol/gsulfanilic acid and Pigment Red 254 and drying down the resultingaqueous dispersion), 6 g Disperbyk BYK163 (an amine-functionalizeddispersant available from BYK Chemie), 15 g Joncryl 611 (an acryliccopolymer available from Johnson Polymer, Inc.), and 64 g butyl acetateas solvent were metered into a vessel. To this was added 2 mm glassbeads, and a dispersion was prepared by mixing on a Skandex mixer. Theglass beads were removed using a paint strainer. The viscosity of thedispersion (15% pigment loading) was measured using a Brookfieldviscometer (spindle 000) and found to be 1.7 cP at 100 RPM. The meanvolume particle size (mV) of the particulate material in the dispersionwas measured using a Microtrac® Particle Size Analyzer and found to be0.19 μm. This dispersion, which included an acrylic copolymer, could beused as a non-aqueous coating composition.

Example 4

15.0 g of a modified colored pigment (prepared by drying Cab-O-Jet® 554Bcolored pigment dispersion, an aqueous dispersion of a modified pigmentcomprising a violet pigment having attached sulfonic acid groupscommercially available from Cabot Corporation), 6 g Disperbyk BYK163 (anamine-functionalized dispersant available from BYK Chemie), 15 g Joncryl611 (an acrylic copolymer available from Johnson Polymer, Inc.), and 64g butyl acetate as solvent were metered into a vessel. To this was added2 mm glass beads, and a dispersion was prepared by mixing on a Skandexmixer. The glass beads were removed using a paint strainer. Theviscosity of the dispersion (15% pigment loading) was measured using aBrookfield viscometer (spindle 000) and found to be 1.5 cP at 100 RPM.The mean volume particle size (mV) of the particulate material in thedispersion was measured using a Microtrac® Particle Size Analyzer andfound to be 0.23 μm. This dispersion, which included an acryliccopolymer, could be used as a non-aqueous coating composition.

Example 5

28.8 g of a modified pigment comprising a carbon black having attachedsulfonic acid groups (prepared using 6 μmol/m² sulfanilic acid andRegal® 330 carbon black and drying down the resulting aqueousdispersion), 15.0 g Solsperse 32500 (an amine-functionalized dispersantavailable from Noveon), 94 g Dowanol PM (available from Dow) as solvent,7.5 g tri(propylene glycol) diacrylate, and 15 g pentaerythritoltriacrylate were metered into a vessel. To this was added 2 mm glassbeads, and a dispersion was prepared by mixing on a Skandex mixer. Theglass beads were removed using a paint strainer. The viscosity of thedispersion (18% pigment loading) was measured using a Brookfieldviscometer (spindle 18) and found to be 6.48 cP at 100 RPM. The meanvolume particle size (mV) of the particulate material in the dispersionwas measured using a Microtrac® Particle Size Analyzer and found to be0.074 μm. This dispersion, which includes curable monomers, could beused as a curable ink composition for industrial inkjet printing.

Example 6

8.8 g of a modified pigment comprising a carbon black having attachedsulfonic acid groups (prepared using 6 μmol/m² sulfanilic acid andRegal® 330 carbon black and drying down the resulting aqueousdispersion), 4.5 g Solsperse 32500 (an amine-functionalized dispersantavailable from Noveon), 28.9 g Dowanol PM (available from Dow) assolvent, 2.3 g tri(propylene glycol) diacrylate, and 4.5 gpentaerythritol triacrylate were metered into a vessel. To this wasadded 2 mm glass beads, and a dispersion was prepared by mixing on aSkandex mixer. The glass beads were removed using a paint strainer. Theviscosity of the dispersion (18% pigment loading) was measured using aBrookfield viscometer (spindle 18) and found to be 6.48 cP at 100 RPM.The mean volume particle size (mV) of the particulate material in thedispersion was measured using a Microtrac® Particle Size Analyzer andfound to be 0.074 μm. This dispersion, which includes curable monomers,could be used as a curable ink composition for industrial inkjetprinting.

Example 7

20 g of a modified pigment comprising a carbon black having attachedsulfonic acid groups (prepared using 6 μmol/m² sulfanilic acid andRegal® 330 carbon black and drying down the resulting aqueousdispersion), 4 g Solsperse 20000 (an amine-functionalized dispersantavailable from Noveon), and 100 g methanol as solvent were metered intoa vessel. To this was added 2 mm glass beads, and a dispersion wasprepared by mixing on a Skandex mixer. The glass beads were removedusing a paint strainer. The viscosity of the dispersion (16% pigmentloading) was measured using a Brookfield viscometer (spindle S00) andfound to be 18.0 cP at 100 RPM. The sample was subjected to acceleratedaging at 50° C. for 36 hours, and the viscosity after accelerated agingwas found to be 19.0 cP.

Example 8

9.98 g of a modified pigment comprising a carbon black having attachedsulfonic acid groups (prepared using 6 μmol/m² sulfanilic acid andRegal® 330 carbon black and drying down the resulting aqueousdispersion), 2.12 g Tergitol L-61 (a non-ionic polyether polyoldispersant available from Noveon), and 100 g methanol as solvent weremetered into a vessel. To this was added 2 mm glass beads, and adispersion was prepared by mixing on a Skandex mixer. The glass beadswere removed using a paint strainer. The viscosity of the dispersion (9%pigment loading) was measured using a Brookfield viscometer (spindleS00) and found to be 2.5 cP at 100 RPM. Similar properties resulted whenthe ethylene glycol solvent was excluded. Therefore, it would beexpected that, if the amount of pigment was increased to 10% loading inthis formulation, similar results would also be observed.

Example 9

8.88 g of a modified pigment comprising a carbon black having attachedsulfonic acid groups (prepared using 6 μmol/m² sulfanilic acid andRegal® 330 carbon black and drying down the resulting aqueousdispersion), 0.82 g Solsperse 20000 (an amine-functionalized dispersantavailable from Noveon), and 40.84 g methanol and 49.5 g ethylene glycolas solvent were metered into a vessel. To this was added 2 mm glassbeads, and a dispersion was prepared by mixing on a Skandex mixer. Theglass beads were removed using a paint strainer. The mean volumeparticle size (mV) of the particulate material in this dispersion (9%pigment loading) was measured using a Microtrac® Particle Size Analyzerand found to be 0.015 μm. The sample was subjected to accelerated heataging at 50° C. for 3 days, and the mean volume diameter particle sizewas found to be 0.015 μm. Similar properties resulted when the ethyleneglycol solvent was excluded. Therefore, it would be expected that, ifthe amount of pigment was increased to 10% loading in this formulation,similar results would also be observed.

Example 10

20.1 g of a modified colored pigment comprising a yellow pigment havingattached sulfonic acid groups (prepared by drying Cab-O-Jet® 270Ycolored pigment dispersion, an aqueous dispersion of a modified pigmentcomprising a yellow pigment having attached sulfonic acid groupscommercially available from Cabot Corporation), 13.5 g Disperbyk BYK163(an amine-functionalized dispersant available from BYK Chemie), and 100g n-butyl propionate as solvent were metered into a vessel. To this wasadded 2 mm glass beads, and a dispersion was prepared by mixing on aSkandex mixer. The glass beads were removed using a paint strainer. Theviscosity of the dispersion (15% pigment loading) was measured using aBrookfield viscometer (spindle 18) and found to be 18 cP at 100 RPM. Themean volume particle size (mV) of the particulate material in thedispersion was measured using a Microtrac® Particle Size Analyzer andfound to be 0.37 μm. The sample was subjected to accelerated heat agingat 50° C. for 3 days, and the mean volume diameter particle size wasfound to be 0.37 μm.

Example 11

19.9 g of a modified colored pigment comprising a magenta pigment havingattached carboxylic acid groups (prepared using 0.7 mmol/g p-aminobenzoic acid and Pigment Red 122 and drying down the resulting aqueousdispersion), 13.2 g Disperbyk BYK163 (an amine-functionalized dispersantavailable from BYK Chemie), and 101 g n-butyl propionate as solvent weremetered into a vessel. To this was added 2 mm glass beads, and adispersion was prepared by mixing on a Skandex mixer. The glass beadswere removed using a paint strainer. The viscosity of the dispersion(15% pigment loading) was measured using a Brookfield viscometer(spindle 18) and found to be 11 cP at 60 RPM.

Example 12

10.8 g of a modified colored pigment (prepared by drying Cab-O-Jet® 740colored pigment dispersion, an aqueous dispersion of a modified pigmentcomprising a yellow pigment having attached sulfonic acid groupscommercially available from Cabot Corporation), 3.8 g Anti-Terra U (asalt of an unsaturated polyamine amide and lower molecular acidavailable from BYK Chemie), and 60 g 1-methoxy-2-propanol as solventwere metered into a vessel. To this was added 2 mm glass beads, and adispersion was prepared by mixing on a Skandex mixer. The glass beadswere removed using a paint strainer. The viscosity of the dispersion(14% pigment loading) was measured using a Brookfield viscometer(spindle 18) and found to be 11 cP at 60 RPM.

Comparative Example 1

17 g Regal® 250 carbon black (commercially available from CabotCorporation), 3.06 g Tergitol L-61 (a non-ionic polyether polyolavailable from Noveon), and 100 g ethylene glycol as solvent weremetered into a vessel. To this was added 2 mm glass beads, and, uponmixing, a paste was formed. Thus, while the loading level was similar tothat of Examples 1-12 (14% pigment loading), no dispersion having lowviscosity resulted.

The foregoing description of preferred embodiments of the presentinvention has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Modifications and variationsare possible in light of the above teachings, or may be acquired frompractice of the invention. The embodiments were chosen and described inorder to explain the principles of the invention and its practicalapplication to enable one skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto, and theirequivalents.

1. A dispersion comprising a particulate material and a solvent, whereina) the particulate material is present in an amount of ≧25% by weightbased on the total weight of the dispersion; b) the solvent has adielectric constant of ≦50; and c) the dispersion has a viscosity of ≦50cP.
 2. The dispersion of claim 1, wherein the dispersion furthercomprises a dispersant which forms associative structures in thesolvent.
 3. The dispersion of claim 2, wherein the dispersion furthercomprises associative structures of the dispersant.
 4. The dispersion ofclaim 1, wherein the particulate material comprises a blue pigment, ablack pigment, a brown pigment, a cyan pigment, a green pigment, a whitepigment, a violet pigment, a magenta pigment, a red pigment, a yellowpigment, an orange pigment, or mixtures thereof.
 5. The dispersion ofclaim 1, wherein the particulate material is an oxidized carbonaceousmaterial.
 6. The dispersion of claim 1, wherein the particulate materialis a modified pigment comprising a pigment having attached at least oneorganic group, wherein the organic group comprises at least one ionicgroup, at least one ionizable group, or a mixture thereof.
 7. Thedispersion of claim 6, wherein the pigment is a carbonaceous pigment oran organic colored pigment.
 8. The dispersion of claim 6, wherein thepigment comprises a blue pigment, a black pigment, a brown pigment, acyan pigment, a green pigment, a white pigment, a violet pigment, amagenta pigment, a red pigment, a yellow pigment, an orange pigment, ormixtures thereof.
 9. The dispersion of claim 6, wherein the organicgroup comprises at least one carboxylic acid group, at least onesulfonic acid group, or salts thereof.
 10. The dispersion of claim 6,wherein the organic group is a —C₆H₄—COOH group, a —C₆H₄—SO₃H group, orsalts thereof.
 11. The dispersion of claim 2, wherein the particulatematerial is a modified pigment comprising a pigment having attached atleast one anionic group, at least one anionizable group, or a mixturethereof and wherein the dispersant comprises at least one cationicfunctional group, at least one cationizable functional group, or amixture thereof.
 12. The dispersion of claim 2, wherein the particulatematerial is a modified pigment comprising a pigment having attached atleast one cationic group, at least one cationizable group, or a mixturethereof and wherein the dispersant comprises at least one anionicfunctional group, at least one anionizable functional group, or amixture thereof.
 13. The dispersion of claim 2, wherein the particulatematerial is a modified pigment comprising a pigment having attached atleast one ionic group, at least one ionizable group, or a mixturethereof and wherein the dispersant comprises at least one nonionicfunctional group.
 14. The dispersion of claim 2, wherein the particulatematerial is a modified pigment comprising a pigment having attached atleast one anionic group, at least one anionizable group, or a mixturethereof and wherein the dispersant comprises at least one anionicfunctional group, at least one anionizable functional group, or amixture thereof.
 15. The dispersion of claim 1, wherein the solvent isan alcohol, an ether, a ketone, an ester, an amide, a sulfoxide, ahydrocarbon, or a miscible mixture thereof.
 16. The dispersion of claim1, wherein the solvent further comprises ≦20% by weight water.
 17. Acoating composition comprising the dispersion of claim
 1. 18. An inkcomposition comprising the dispersion of claim
 1. 19. The inkcomposition of claim 18, wherein the ink composition is a non-aqueousinkjet ink composition.
 20. A black matrix composition comprising thedispersion of claim
 1. 21. A dispersion comprising a particulatematerial, a dispersant, and a solvent, wherein a) the particulatematerial is an oxidized carbonaceous material or a modified pigmentcomprising a pigment having attached at least one ionic group, at leastone ionizable group, or a mixture thereof; b) the dispersant formsassociative structures in the solvent; c) the solvent has a dielectricconstant of ≦50; and d) the dispersion has a viscosity of ≦50 cP,wherein the particulate material is present in an amount of ≧10% byweight based on the total weight of the dispersion.
 22. The dispersionof claim 21, wherein the particulate material is present in an amount of≧20% by weight based on the total weight of the dispersion.
 23. Thedispersion of claim 21, wherein the dispersion further comprisesassociative structures of the dispersant.
 24. The dispersion of claim21, wherein the pigment is a carbonaceous pigment or an organic coloredpigment.
 25. The dispersion of claim 21, wherein the pigment comprises ablue pigment, a black pigment, a brown pigment, a cyan pigment, a greenpigment, a white pigment, a violet pigment, a magenta pigment, a redpigment, a yellow pigment, an orange pigment, or mixtures thereof. 26.The dispersion of claim 21, wherein the organic group comprises at leastone carboxylic acid group, at least one sulfonic acid group, or saltsthereof.
 27. The dispersion of claim 21, wherein the organic group is a—C₆H₄—COOH group, a —C₆H₄—SO₃H group, or salts thereof.
 28. Thedispersion of claim 21, wherein the particulate material is a modifiedpigment comprising a pigment having attached at least one anionic group,at least one anionizable group, or a mixture thereof and wherein thedispersant comprises at least one cationic functional group, at leastone cationizable functional group, or a mixture thereof.
 29. Thedispersion of claim 21, wherein the particulate material is a modifiedpigment comprising a pigment having attached at least one cationicgroup, at least one cationizable group, or a mixture thereof and whereinthe dispersant comprises at least one anionic functional group, at leastone anionizable functional group, or a mixture thereof.
 30. Thedispersion of claim 21, wherein the particulate material is a modifiedpigment comprising a pigment having attached at least one ionic group,at least one ionizable group, or a mixture thereof and wherein thedispersant comprises at least one nonionic functional group.
 31. Thedispersion of claim 21, wherein the particulate material is a modifiedpigment comprising a pigment having attached at least one anionic group,anionizable group, or a mixture thereof and wherein the dispersantcomprises at least one anionic functional group, at least oneanionizable functional group, or a mixture thereof.
 32. The dispersionof claim 21, wherein the solvent is an alcohol, an ether, a ketone, anester, an amide, a sulfoxide, a hydrocarbon, or a miscible mixturethereof.
 33. The dispersion of claim 21, wherein the solvent furthercomprises ≦20% by weight water.
 34. A coating composition comprising thedispersion of claim
 21. 35. An ink composition comprising the dispersionof claim
 21. 36. The ink composition of claim 35, wherein the inkcomposition is a non-aqueous inkjet ink composition.
 37. A black matrixcomposition comprising the dispersion of claim
 21. 38. A dispersioncomprising a particulate material, a dispersant, and a solvent, whereina) the particulate material is an oxidized carbonaceous material or is amodified pigment comprising a pigment having attached at least one ionicgroup, at least one ionizable group, or a mixture thereof; b) thedispersant forms associative structures in the solvent; c) the solventhas a dielectric constant of ≦50; and d) the dispersion has a viscosityof ≦50 cP, wherein the dispersion further comprises associativestructures of the dispersant.